1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device and a semiconductor device manufactured thereby and, more specifically, to improvement of a high-pressure reflow process for formation of interconnections of a semiconductor device.
2. Background Art
A conventional manufacturing method of a semiconductor device and the structure of a resulting semiconductor device will be described with reference to FIGS. 3(a)-3(c).
FIG. 3(a) illustrates the formation in a semiconductor wafer 10, of an interlayer insulating film 2 on a semiconductor substrate 1 (silicon substrate) on which a semiconductor element (not shown) is formed. Subsequently, a wiring groove 3 and a connection hole 3a are formed capable of electrically connecting the semiconductor element on the semiconductor substrate 1 to an upper-layer interconnection (not shown) formed on the interlayer insulating film 2.
Then, the semiconductor wafer 10 (under manufacture) is placed in a low-pressure atmosphere to remove water, etc. absorbed on the surface, and the temperature is increased. If necessary, the surface of the wafer 10 is thereafter cleaned by etching it by argon inverse sputtering.
Then, a copper film 5 is formed by sputtering. At this time, as shown in FIG. 3(b), a void 8 is formed at the bottom of the connection hole 3a in the wiring groove 3 of the semiconductor wafer 10.
Subsequently, while the semiconductor wafer 10 is heated to 400.degree. C. or higher, a high pressure of about 40-100 MPa is applied. The copper is caused to flow into the void 8, and the inside of the wiring groove 3 and the connection hole 3a is charged with copper.
As shown in FIG. 3(c), the copper film 5 is oxidized (by oxygen or water included in an argon gas) for the application of a high pressure, forming copper oxide film 7 on the surface of the copper film 5. The oxidation of the copper film S is not limited to its surface, and oxygen diffuses into the inside of the copper film 5. Thus, the flowability of copper during the application of a high pressure is lowered. As a result, as shown in FIG. 3(c), the void 8 remains even after the high-pressure treatment. That is, filling failure occurs.